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<head><meta charset="utf-8"><title>Intuition for `DatafrogOpt` · t-compiler/wg-polonius · Zulip Chat Archive</title></head>
<h2>Stream: <a href="https://rust-lang.github.io/zulip_archive/stream/186049-t-compiler/wg-polonius/index.html">t-compiler/wg-polonius</a></h2>
<h3>Topic: <a href="https://rust-lang.github.io/zulip_archive/stream/186049-t-compiler/wg-polonius/topic/Intuition.20for.20.60DatafrogOpt.60.html">Intuition for `DatafrogOpt`</a></h3>

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<a name="221365856"></a>
<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/186049-t-compiler/wg-polonius/topic/Intuition%20for%20%60DatafrogOpt%60/near/221365856" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> Dylan MacKenzie (ecstatic-morse) <a href="https://rust-lang.github.io/zulip_archive/stream/186049-t-compiler/wg-polonius/topic/Intuition.20for.20.60DatafrogOpt.60.html#221365856">(Jan 01 2021 at 19:49)</a>:</h4>
<p>Am I correct that <a href="https://github.com/rust-lang/polonius/issues/23">rust-lang/polonius#23</a> is the genesis of the <code>DatafrogOpt</code> ruleset? I stared at it for a while but couldn't figure out what was going on before looking through the git history and finding that PR.</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/186049-t-compiler/wg-polonius/topic/Intuition%20for%20%60DatafrogOpt%60/near/221372471" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lqd <a href="https://rust-lang.github.io/zulip_archive/stream/186049-t-compiler/wg-polonius/topic/Intuition.20for.20.60DatafrogOpt.60.html#221372471">(Jan 01 2021 at 22:37)</a>:</h4>
<p>absolutely</p>



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<h4><a href="https://rust-lang.zulipchat.com#narrow/stream/186049-t-compiler/wg-polonius/topic/Intuition%20for%20%60DatafrogOpt%60/near/221372760" class="zl"><img src="https://rust-lang.github.io/zulip_archive/assets/img/zulip.svg" alt="view this post on Zulip" style="width:20px;height:20px;"></a> lqd <a href="https://rust-lang.github.io/zulip_archive/stream/186049-t-compiler/wg-polonius/topic/Intuition.20for.20.60DatafrogOpt.60.html#221372760">(Jan 01 2021 at 22:45)</a>:</h4>
<p>the intuition I have (and note that I don't understand this variant as well as I should) is that the vast majority of subsets are local and involve dead origins (that is, they mostly participate in propagating loans at a single point), and the origins of interest (especially in the NLL case) at least involved dying along an edge (so that both subsets and loans were to be propagated down the CFG) -- and which I like to call "differential liveness" -- so this is where this variant focuses the TC</p>



<hr><p>Last updated: Aug 07 2021 at 22:04 UTC</p>
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